In the last decade the production of single-cell protein(SCP) from C.sub.1 -compounds has been studied extensively both by academic and industrial laboratories. Enterprises such as Mitsubishi Gas Chemical Co., Hoechst, and I.C.I. have implemented pilot plant studies, but to date only I.C.I. is operating a full scale SCP plant. "Pruteen" is the registered trademark of the I.C.I. product and is made by the fermentation of the obligate methylotrophic bacterium, Methylophilus methylotrophus, which is eventually separated and dried to a powder or granules Methylophilus methylotrophus is an obligate methylotroph which uses the ribulose monophosphate pathway(RMP) cycle of formaldehyde fixation. Methylophilus methylotrophus kStrain AS-1 is a gram negative, nonpigmented rod with a single polar flagellum.
In SCP production, methanol feedstock constitutes the highest percentage of the operating costs, so that any increase in the microbial growth rate yield has a direct influence on the operating costs of the SCP production. For this reason I.C.I. has applied recombinant DNA technology to increase the cell yield by altering the genome of the Methylophilus methylotrophus microorganism. The genes for the more efficient glutamate dehydrogenase nitrogen assimilation system from Escherichia coli were cloned and inserted into a Methylophilus methylotrophus strain. This strain previously had its less efficient glutamate synthase nitrogen assimilation system blocked by means of DNA mutation, as described by J. Windass et in Nature, 287 396(1980).
Although methanol generally is viewed as a substrate for the production of single cell protein, the factors that qualify it for SCP manufacture also recommend methanol as a potential feedstock for the production of accumulated extracellular metabolites such as exopolysaccharides. A number of microbial processes for the conversion of methanol to value-added products have been described but generally these are low-volume/high-priced compounds such as aminoacids. Thus, J. Bolbot and C. Anthony in Proc. Soc. Gen. Microbial, 5, 43(1978) found that a pyruvate dehydrogenase lacking mutant of Pseudomonas AMI could accumulate the aminoacids alanine and valine during growth on methanol Y. Tani et al in Agric. Biol Chem., 42, 2275(1978) have described the production of up to 5.2 grams per liter of L-serine from methanol employing an Arthrobacter globiformis strain. Up to the present time there has not been any report of methanol bioconversion to a commodity type of bulk chemical.
Accordingly, it is an object of this invention to provide a fermentation process for the bioconversion of a C.sub.1 -compound to an accumulated quantity of extracellular metabolite.
It is another object of this invention to provide a rapid growth culture medium for bio-oxidation of a methanol substrate to an accumulated quantity of an exopolysaccharide.
It is another object of this invention to provide a novel facultative methylotroph species.
It is another object of this invention to provide methylotrophic microorganism strains having the identifying characteristics of strain ATCC 39893 .
It is a further object of this invention to provide a novel heteropolysaccharide which exhibits properties suitable for imparting pseudoplastic and thixotropic properties to aqueous solutions.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.